@(#)network speed comparison howto 06 AUG 1997 Rob Thomas robt@cymru.com
Howto figure out how fast your link is compared to other links.

It's always a *bit* confusing when network weenies throw a lot of figures
at you.  "Hey, this is full T1, man!  It rocks!"  Er, OK, but does it
really rock?  How does it compare in terms of raw throughput to your
current 10 Base T LAN?  Where will your network bottleneck exist?

Folks are generally very surprised when I make a lowest-common denominator
comparison of the different network speeds.  Mind you, this is really not
an apples-to-apples comparison.  Although 10Mbit Ethernet is in theory faster
than T1, a T1 link does not suffer the overhead of CSMA/CD.  Keep the
fundamental media differences in mind while reading this page.

All figures are ROUGH guesstimates for comparison use only.  This ain't
gospel, folks, just estimates.

1. Full DS1 Serial Link.
   A DS1 link operates at 1.544 megabits/second.  That translates to:
   - 193,000 bytes/second.
   - 193 kilobytes/second.

2. Full DS3 Serial Link.
   A DS3 link operates at 45 megabits/second.  That translates to:
   - 5,625,000 bytes/second.
   - 5625 kilobytes/second.

3. 2B+D 128K ISDN Link.
   A dual-channel ISDN link operates at 128 kilobits/second.  That translates
   to:
   - 16000 bytes/second.
   - 16 kilobytes/second.

4. 56K Serial Link.
   A 56K link operates at 56 kilobits/second.  That translates to:
   - 7000 bytes/second.
   - 7 kilobytes/second.

5. 56K modem (which, by FCC rules, can operate only at 53K).
   A 56K modem (USR or Motorola) operates at a top speed of 53 kilobits/second.
   That translates to:
   - 6625 bytes/second.
   - 6.6 kilobytes/second.

6. 10 Base T network.
   A 10 Base T network operates, theoretically, at 10 megabits/second.
   That translates to:
   - 1,250,000 bytes/second.
   - 1250 kilobytes/second.

7. FDDI/CDDI or 100 Base T network.
   A FDDI network operates, theoretically, at 100 megabits/second.  They do
   NOT operate in a similar fashion, however (token versus CSMA/CD, etc.).
   That translates to:
   - 12,500,000 bytes/second.
   - 12500 kilobytes/second.

8. 33.6K modem.
   A 33.6K modem operates at a top speed of 33.6 kilobits/second.  That 
   translates to:
   - 4200 bytes/second.
   - 4 kilobytes/second.

As always, questions/comments/bugs to: robt@cymru.com

Rob Thomas, robt@cymru.com
http://www.enteract.com/~robt